SEISMIC STABILIZED HIGH RAIL CRANES

摘要

SEISMIC STABILIZED HIGH-RAIL CRANES Cranes for polar or linear movement on highly elevated rails or runways as, for example, on the circular top of a containment tower building for a nuclear reactor and/or on the highly elevated linear tracks on top of the parallel walls of the turbine room adjacent such a containment tower, hereinafter sometimes called high-rail cranes, which cranes, if not protected against earthquack shocks as transmitted and amplified by such towers and walls,could be injured and caused to drop their loads or trolleys or fall bodily from their supporting rails or runways. Such a calamitous failure would likely cause catastrophic damage to the nuclear reactor, and/or the fuel vessel or cask, with probable release of dangerous radiation, hopefully to be confined within the tower if it too has not been injured and breached. Protection against such earthquake shocks and failures is provided in many forms of my invention by one or more horizontal structural members which comprise a seismic stabilizer or more than one seismic stabilizer and which connects or connect the bridge girders of the crane with the said rail or runway at points spaced or remote from the ends of the crane. In connecting the crane bridge girders with the building runway by the stabilizer, the natural resonant frequency of the crane bridge girders is increased due to more points of restraint and due to increasing the effective stiffness of the girders by the seismic stabilizer or stabilizers. The seismic stabilizers add restraint points to the, span of the bridge girders, and consequently change the resonant response of the girders from the first mode shape of the natural resonant frequency of unstabilized girders to higher mode shapes resulting in higher frequencies. This prevents the girders from resonating with the seismic frequency of the earthquake shock and preserves the crane, its load and the trolley, as well as the tower and its contents including the reactor. In other forms of my invention, the bridge girders themselves may take self-stabilizing forms such as Y or T forms as viewed in horizontal plan, having at least three points of support on their supporting circular rails in the first instance.